A camera accessory (hereinafter referred to just as an accessory) receives power supply from a camera and exchanges a command, data, and the like with the camera in a state mounted on the camera. A plurality of contacts, which is electrically connected by making a contact with each other, is formed at mounting portions (mounts) of the camera and the accessory to allow the power supply and communication. Further, in many cases, a bayonet coupling method is employed for attachment (coupling) between the camera and the accessory. According to the bayonet coupling method, a relative rotation is performed between the mounts of the camera and the accessory to engage bayonet teeth provided on the respective mounts with each other.
Japanese Patent Application Laid-Open No. 62-195633 discusses a camera and an interchangeable lens respectively including mounts configured to be attached to each other by the bayonet coupling method. When the camera and the interchangeable lens are in a coupling completion state after a relative rotation between the mounts of the camera and the interchangeable lens, a plurality of camera-side contact pins provided on the camera-side mount and a plurality of lens-side contact pins (contact surfaces) provided on the lens-side mount are in contact with each other. The camera-side contact pins and the lens-side contact pins are held by contact seats provided on the mounts. A hole for holding the camera-side contact pin is formed at the camera-side contact seat. A spring, which biases the camera-side contact pin in a direction causing the camera-side contact pin to project from the hole, is disposed between the camera-side contact pin inserted in the hole and a bottom surface (a printed wiring board) of the hole. On the other hand, the lens-side contact pin is fixed to the lens-side contact seat.
In recent years, the mount has been formed by molding for the purpose of reducing a weight of the camera. Hereinafter, the mount mold-formed in this manner will be referred to as a molded mount. Further, in some cases, a plate spring may be used as the contact spring, which biases the camera-side electric contact pin in the projecting direction, for the purpose of reducing a thickness of the camera.
Further, the camera-side and lens-side contact pins include a power supply contact pin for supplying power from the camera to the accessory to drive an actuator in the accessory, and a control contact pin for exchanging a signal to control the accessory.
There are following problems in the camera and the accessory having the mounts (especially, the molded mounts) provided with the contact pins as described above.
FIG. 19 illustrates a camera 401 with an interchangeable lens 402 as an accessory mounted thereon when the camera 401 is dropped onto a ground surface 405. When the camera 401 is dropped, it is highly likely that a tip of the interchangeable lens 402 which is heavier hits against the ground surface 405 first. In this case, a maximum external force for pulling off mounts is generated at lowermost portions of the mounts that couple the camera 401 with the interchangeable lens 402. Therefore, it is desirable to dispose an engagement portion of bayonet teeth, and attachment portions using fastening screws for respectively attaching the camera-side mount and the lens-side mount to a camera main body and an interchangeable lens main body at a phase including the lowermost portions of the camera-side and lens-side mounts.
However, in a case where the camera-side contact pin is provided at the same position as the fastening screw in a mount circumferential direction, and the plate spring is used as the contact spring for biasing the camera-side contact pin in the projecting direction, the plate spring should be disposed so as to avoid the fastening screw, which leads to the necessity of increasing a pitch between the contact pins. This results in an increase in an angular range occupied by the contact pins at the mount, hindering a reduction in the size of the camera.
On the other hand, the camera includes a motor as an actuator for driving, for example, a shutter, and noises generated by this motor may affect control of the lens-side accessory which causes a malfunction of the accessory.
Further, wiring is laid from a power source circuit to the power supply contact pin provided at the camera via a flexible board or the like. If the length of this wiring is long, a loss due to a wiring resistance may increase.